Coexistence of Type-I and Type-II Weyl Points in the Weyl-Semimetal OsC₂

Abstract

The topologically nontrivial Weyl semimetals have two different types: (i) the standard Weyl cones with point-like Fermi surfaces (type-I) and (ii) tilted Weyl cones that appear at the contact of electron and hole pockets (type-II). These two types of Weyl semimetals have significantly different physical properties in their thermodynamics and magnetotransport. Here we presented a compound OsC2 with both types Weyl points (WPs) at the equilibrium volume. It has 24 type-I WPs in the K z = ±0.0241 planes around K (or K′) points and 12 type-II WPs in the K z = ±0.4354 planes at the projected K (K′) point, respectively. The type-I WPs are connected by the helix-trimer Fermi arcs.

Linear magnetochiral transport in tilted type-I and type-II Weyl semimetals

“…Depending on the broken inversion or time reversal symmetry (TRS), the two Weyl nodes (WNs) of opposite chirality are separated either in energy or momentum. Unlike their high-energy counterparts, the WNs in condensed matter systems can also be anisotropic and tilted (called type-I) or tilted over (type-II) [14][15][16][17][18][19][20][21], as shown in Fig. 1.…”

Hexagonal Zr3X (X = Al, Ga, In) Metals: High Dynamic Stability, Nodal Loop, and Perfect Nodal Surface States

“…The dimensionality of band-crossings is a criterion used to classify topological semimetals/metals. The most famous topological semimetals/metals with zero-dimensional band-crossings, i.e., zero-dimensional nodal points, are Dirac semimetals/metals (Chen et al, 2015(Chen et al, , 2020Bradlyn et al, 2017;Zhong et al, 2017;Jing and Heine, 2018;Liu et al, 2018b;Zhang et al, 2018b;Khoury et al, 2019;Wang et al, 2020f;Xu et al, 2020) and Weyl semimetals/metals (Peng et al, 2016;Lin et al, 2017;Fu et al, 2018;Zhang et al, 2018c;Zhou et al, 2019;Gupta et al, 2020;Jia et al, 2020;Liu et al, 2020;Meng L. et al, 2020;Zhao B. et al, 2020). We selected Weyl semimetals/metals as examples here because there exists a band-crossing of the valance band and conduction band at an isolated nodal point in the momentum space of these solids.…”

Berry curvature induced thermopower in type-I and type-II Weyl semimetals

“…Unlike their relativistic counterparts, in crystalline systems the Weyl quasiparticles can also break Lorentz invariance. Consequently, their dispersion can be tilted in a specific direction [10][11][12][13][14][15][16][17][18] . Depending on the degree of the tilt, these WSMs can be classified as type-I or type-II.…”